Wireless Electronic Vehicle Charging (WEVC) from a ground-based unit to a vehicle-mounted pick-up unit generally requires foreign object detection (FOD). Conventional FOD systems can fail to detect certain small ferromagnetic objects having a length substantially longer than a thickness, such as nails, pins, steel wire pieces, staples, and so forth. These small objects have the potential of reaching hazardous temperatures if exposed to magnetic fields in the millitesla range and with an orientation substantially in a direction of the magnetic field.
Because of these challenges, inductive ferromagnetic sensing (IFS) has been used to detect ferromagnetic objects. The achievable sensitivity of IFS, however, is limited to paperclip-size objects, and are not sufficient for tiny steel wire pieces, fixing pins, nails, and so forth. Thermal sensing using an infrared (IR) camera is yet another alternative solution used to detect ferromagnetic objects. IR sensing, however, cannot accurately detect small hot objects shadowed by another cold object.